Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Quantos se inscreveram quando a matrícula era 1150 em Sioux City, Iowa?
 ###Tabelas: CREATE TABLE rs_series_b-b (rs_series_b-b_id AUTO_INCREMENT PRIMARY KEY, Model VARCHAR, Specification VARCHAR, Build date VARCHAR, Total produced INT, Wheel arrangement VARCHAR, Prime mover VARCHAR, Power output VARCHAR) CREATE TABLE current_members (current_members_id AUTO_INCREMENT PRIMARY KEY, Institution VARCHAR, Location VARCHAR, Founded INT, Type VARCHAR, Enrollment INT, Joined INT, Nickname VARCHAR) CREATE TABLE result (result_id AUTO_INCREMENT PRIMARY KEY, Office VARCHAR, Democratic ticket VARCHAR, Republican ticket VARCHAR, Law Preservation ticket VARCHAR, Socialist ticket VARCHAR, Socialist Labor ticket VARCHAR) CREATE TABLE base_salary (base_salary_id AUTO_INCREMENT PRIMARY KEY, GS Grade INT, Step 1 VARCHAR, Step 2 VARCHAR, Step 3 VARCHAR, Step 4 VARCHAR, Step 5 VARCHAR, Step 6 VARCHAR, Step 7 VARCHAR, Step 8 VARCHAR, Step 9 VARCHAR, Step 10 VARCHAR) CREATE TABLE touchdowns (touchdowns_id AUTO_INCREMENT PRIMARY KEY, Player VARCHAR, Rec. INT, Yards INT, Avg. INT, TD's INT, Long INT)  
SELECT Joined FROM current_members WHERE Enrollment = 1150 AND Location = Sioux City, Iowa